By Ruth Vaughan, Msc. Applied Science
Today is World Soil Day. However, Africa continues to be affected by hunger and low crop yields. Populations are increasing and soil fertility is dropping. Traditional farming methods relied on larger areas of land and long periods of fallow but, with increasing pressure on the land this is no longer possible. There is a huge opportunity and need for yield intensification, how can we achieve this?
The soil is one of the most important assets farmers have. Soil is unique in every farm and field — dynamic, alive and constantly changing due to an interconnected web of physical, chemical and biological relationships that determine the health of the soil, the crops, the livestock and the people. Maintaining healthy soils by improving soil structure, nutrient content and biological activity, will bring in higher yields with less inputs, i.e. higher profits, as well as minimizing the negative impacts on the environment that can follow poor soil management.
Where do we start? The best place w start is at the beginning: have a complete soil analysis performed by a reputable laboratory. This will give you an idea of the current status of the soil and should include EC, pH, the major and minor elements, the organic matter content and the inherent ‘fertility’ of the soil_ At this stage it is also good to get a one-off idea of your soil type (clay, loam, sandy). A good laboratory or agronomist should give you recommendations for liming or gypsum application, rock phosphate and manure/compost applications.
Mineralize – feed your soils and unlock their potential!
Liming or gypsum application will balance the pH and the calcium and magnesium levels in the soil, which in turn will improve the soil structure and microbial activity. In many places in Kenya the soils are very acidic and large amounts of lime are required. In this case a soil improvement program can be put in place where the application rates are spread over a number of years according to budget.
Rock phosphate is mined in East Africa and therefore much cheaper than soluble mineral fertilizers, that are imported. This saves you money. Rock phosphate dust is mixed into the soil, so that it is distributed throughout the soil profile. This is good for soil structure and biological activity (that word again!) and so much better for the plants. Phosphates are very immobile in the soil and difficult for the plant to take up, they are also very often a yield limiting factor in plant growth, so mixing the rock phosphate into the soil makes it easier for the plant roots to take it up as they grow.
Balancing the pH will mean that the soluble/ mineral fertilizers that you apply for your crop will work better for you. In very acidic soil, let’s say pH 4.5, only about 30 percent of the nitrogen, 23 percent of the phosphorous and 33 percent potassium you invest in and apply is available for your crop. The rest is locked up or lost to the environment. It makes huge financial sense therefore to invest at the onset. (Less fertilizer inputs + higher yields = more profits!).
Encourage biological activity
Biological activity is due to the flora (plants) and fauna (animals) in the soil, Most of this is from little guys that we can’t see with the naked eye. Like everything else they need a balanced diet, and the right quantities of air and water. They are most important for recycling organic matter, breaking down the soil mineral structure and making nutrients more available to your plants. Some even fix nitrogen from the air and make it available to the plants.
The more diverse your flora and fauna – the better for you! They are the key to unlocking the nutrients and reducing your pests and diseases. (Less fertilizers + less pesticides + higher yields = more profits!). How does one encourage biological activity? Improving the soil structure means you get a better balance of air and water.
Balancing your pH creates an environment that they can live and breed in. Increasing your organic matter means they have a carbon source to feed on. In some cases they require certain micro elements that may not be present in the soil but need to be added (this is where a compete soil analysis comes in handy). Manures, compost, green manure crops or other carbon sources feeds them and the soil. A good crop rotation program promotes diversity and prevents build- up of pathogens.
Build organic matter
The organic matter (OM) content of your soil plays an enormous role in soil fertility. It fuels the biological activity that is so important for plant nutrient uptake. It holds water – humus holds 4X its weight in water. A 1% increase in Organic matter in your soil will hold an extra 48,000 liters of water, AND at the same time you are playing a positive role against global warming (1% organic matter = 12 tons carbon sequestration).
The organic matter also plays a big role in improving soil structure, pH and buffering the soluble chemical fertilizers that are added, so that they are more available for the crop and less likely to be leached out of the soil. Organic matter helps reduce water erosion and wind erosion of your valuable topsoil. (Less loss + more yield = more profits).
Healthy soils are rewarding soils
Building healthy soils through adapting an integrated soil fertility management approach, where you are feeding the soil, and looking at balancing all aspects of the soil properties: physical, chemical and biological, is very rewarding. It will reduce your reliance on increasingly expensive inputs and result in a highly sustainable and profitable farming operation
Ruth Vaughan is the Technical Director at Crop Nutrition Laboratory Services Ltd. (CROPNUTS). Ruth is also a contributing author to Kenya’s leading horticulture magazines such as the HortFresh Journal, HortiNews and Floriculture. Ruth is a great believer in soil health, organic matter, biochar and carbon sequestration as a way to alleviate climate change and increase food security. Loves visiting farmers and seeing all the different farming methods